Carbon nanotube structure-selective separation and surface fixation

ABSTRACT

A method of separating, concentrating or purifying uniform carbon nanotubes with desired properties (diameter, chiral vector, etc) in a highly sensitive manner by the use of structure-sensitive properties peculiar to carbon nanotubes; and an apparatus therefor. There is provided a method of separating, concentrating, or purifying carbon nanotubes with the desired properties contained in a sample, comprising the steps of (a) irradiating a sample containing carbon nanotubes with light; and (b) selecting carbon nanotubes with desired properties. In a preferred embodiment, the light irradiation of the step (a) can be carried out in the presence of a metal so as to cause specified carbon nanotubes to selectively induce a photocatalytic reaction, resulting in metal deposition. Further, in a preferred embodiment, a given magnetic filed can be applied in the steps (b) so as to attain accumulation or concentration or carbon nanotubes with metal deposited.

TECHNICAL FIELD

The present invention relates to a method and an apparatus for highlyselectively separating, concentrating, and refining carbon nanotubes(CNTs). The invention also relates to a high purity carbon nanotubeseparated by the method of the invention, and a thin film and an arraythereof. The invention further provides an optical device or anelectronic device using the carbon nanotube film.

BACKGROUND ART

A carbon nanotube is a new substance discovered by Sumio Iijima in 1991,which can exhibit a metallic and/or semiconducting property depending onthe diameter thereof and the way the tube is wound. The individualphysical property of the carbon nanotube is entirely different dependingon the structure of the tube, and study within the art is currentlybeing vigorously undertaken. In addition, the carbon nanotube is asubstance, of which much is expected as a next generation material foruse in devices and the like, having applications in the field ofelectronics and energy.

From studies on a process for producing a single-walled carbon nanotube(SWNT), an industrially low-cost mass-production of the carbon nanotube(the Chemical Vapor Deposition or CVD method) has nearly beenestablished, for example, by decomposition of a hydrocarbon usingferrocene as a catalyst (see, for example, Non-Patent Document 1). Assuch, the carbon nanotube has been commercialized. As a representativeexample of a method for synthesizing a single-walled carbon nanotube,there are an arc discharge method and a laser evaporation method (e.g.,see Non-Patent Document 2). The carbon nanotube is further purified byultrafiltration (e.g., see Non-Patent Document 2), wherein a purity of90% or more is obtainable.

The distribution of the diameters of single-walled carbon nanotubesproduced by an arc discharge differs depending on the type of metalcatalyst to be used in the synthesis. In this way, it is possible tocontrol the average diameter of the carbon nanotube by selecting thetype of metal catalyst, and thereby the distribution of the diameter ofthe carbon nanotube produced can be controlled with an average diameterin the range of ±0.4 nm. However, any method among the existingproduction methods does not allow a selective synthesis of asingle-walled carbon nanotube which has a particular diameter.

Therefore, studies for establishing a method for the separation andpurification of certain carbon nanotubes from carbon nanotubes given bythe above-mentioned existing production method, have been carried out inorder to investigate the characteristic physical properties of saidindividual carbon nanotubes separated and purified.

For an example, P. Umek and D. Mihailovic carried out agarose gelelectrophoresis of single-walled carbon nanotubes dispersed in aqueoussodium dodecyl sulfate (SDS) solution, followed by hydrochloric acidtreatment, removal of SDS using deionized water, desiccation, and Ramanspectroscopy examination of the resultant respective fractions. Thisconfirmed that the single-walled carbon nanotubes were partiallyseparated on the basis of diameter and length thereof (see, e.g.,Non-Patent Document 3).

Further, Stephen K. Doom et al. carried out capillary electrophoresis ofa solution of carbon nanotubes dispersed in SDS and found, fromabsorption spectra and Raman spectra of respective separated carbonnanotubes, that the single-walled carbon nanotubes could be separateddepending on differences in the elution time among respective carbonnanotubes, which reflects the difference in the length thereof. (see,e.g., Non-Patent Document 4). The above-mentioned studies have nearlyestablished a method for separating the carbon nanotube based on thelength thereof.

However, the characteristic physical property of the carbon nanotube isdetermined depending on a multiple physical properties such as thediameter and the chiral angle thereof, which means that separation ofcarbon nanotubes based only on the length thereof does not necessarilycorrespond to the separation based on the characteristic physicalproperty thereof. Therefore, to date, the length-based separations ofcarbon nanotubes is not sufficient to define the characteristic physicalproperty thereof.

Although many studies have been performed so far on carbon nanotubes,the precision has still remained very low for the preparation,separation or purification of single-walled tubes which have the samediameter, chirality, work function, and band gap (see, e.g., Non-PatentDocuments 5 to 12). With respect to the resultant separation based ondiameter, Non-Patent Document 9, which discloses a separation of DNA-CNTby ion exchange chromatography, is an example of a related prior art.However, it is completely different in the principle from the presentinvention, and inferior to the technique of the present invention inseparation precision. Further, there are some patent applicationsdirected to a method for purification of a carbon nanotube (see, e.g.,Patent Documents 1 to 5). However, all of these Patent Documents 1 to 5only disclose techniques of impurity removal. Thus these documents donot describe any separation of carbon nanotubes which have a uniformcharacteristic physical property, wherein diameter, chiral angle and thelike thereof, are respectively the same.

Although various studies have contributed to the characterization of theelectron structure of carbon nanotubes, which are dependent on thestructures of respective carbon nanotubes, very limited information isavailable on the absolute potential in the energy level of the carbonnanotube, with the widespread impression that while a monomolecularcarbon nanotube has various structures, the absolute potential of theFermi level of individual carbon nanotubes is considered to be at asimilar level. By investigating spectral features of Raman scattering(especially in the radial breathing mode (w=150-240 cm⁻¹)) of isolatedsingle-walled carbon nanotubes (SWNT) which are metallic orsemiconducting in solution under a potential control, we are the firstin the world to have discovered that the Fermi level of tubes was foundto positively shift greatly with the decrease of tube diameters. Theseobservations suggest that the work function of the tube depends heavilyupon the structure of the SWNT. Further, we also have discovered thatthe structural dependence of a metallic carbon nanotube is significantlylarger than that of a semiconducting carbon nanotube. The greatdifference in the work function means that, for example, a carbonnanotube with a specific diameter is more stable than a noble metal(e.g., Au and Pt), and that on the other hand, a carbon nanotube with alarger diameter has the same degree of tendency to release electrons asMg and Al. Based on the above discussions, it has first been made clearthat the characteristic physical properties of a single carbon nanotubehas a significant dependence upon the diameter, chirality thereof, andthe like.

In order to put carbon nanotubes, which are expected to be the nextgeneration material, into practical utilization, it is inevitablyrequired to control the physical properties dominated by the diameterand chirality thereof, and the like. Therefore, an innovative separationmethod has to be established to sort the carbon nanotube in accordancewith the desired physical properties to be utilized.

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DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention takes advantage of the correlation between thestructure-sensitive electronic energy level of a carbon nanotube and theredox potential of a metal, in order to obtain carbon nanotubes whichhave a desired physical property. The present inventive processcomprises providing different metal ions, which have differentrespective redox potentials, as well as carbon nanotubes which havedifferent respective electronic energy levels, wherein the energy levelsare sensitive to diameter, chirality or the like thereof; and causing aredox reaction between the metal ions and the carbon nanotubes, whichhave an energy band gap enabling the absorption of near-infrared lightin a magnetic field, through excitation by light irradiation to depositthe metals on the surface of the carbon nanotube, thereby precipitatingonly the desired carbon nanotube.

The object of the invention is to provide a method and an apparatus forhighly selectively separating, concentrating or refining carbonnanotubes which have desired physical properties, especially uniformityin at least either a diameter or a chiral vector, by utilizing thestructure-sensitive particular property of the carbon nanotubes.

Another object of the invention is to apply, as a next generationmaterial in electronics and energy fields, a thin film of high puritycarbon nanotubes separated by the above-mentioned method to optical orelectronic devices.

Means for Solving the Problems

The present invention provides the following:

(1) A method of separating, concentrating, or refining a carbon nanotubehaving a desired physical property from a sample, comprising steps of:

a) irradiating light to a sample containing carbon nanotubes and

b) selecting the carbon nanotubes having the desired physical property.

(2) The method according to item (1), wherein said physical propertyincludes at least either a diameter or a chiral vector.

(3) The method according to item (1), wherein said carbon nanotube has asingle-walled structure.

(4) The method according to item (1), wherein said light has a certainwavelength within a range covering from the near infrared region to theultraviolet region.

(5) The method according to item (4), wherein said light ismonochromatic light or laser light having said wavelength.

(6) The method according to item (1), wherein light irradiation in thestep a) is carried out in the presence of metal ions.

(7) The method according to item (6), wherein said metal ion is selectedfrom the group consisting of alkali metals; alkaline earth metals;transition metals selected from the group consisting of Group IIIA toGroup VIIA elements, Group VIII elements, and Group IB elements; andrare earth elements.

(8) The method according to item (1), wherein the step b) is carried outby applying a predetermined magnetic field to said carbon nanotube so asto precipitate the carbon nanotube with the desired physical property.

(9) The method according to item (1), wherein the step b) is carried outby chromatography.

(10) The method according to item (1), wherein said sample furthercontains a surfactant.

(11) The method according to item (10), wherein said surfactant isselected from the group consisting of sodium dodecyl sulfate, sodiumdodecylbenzenesulfonate, Triton X, alkylsulfonates, sodiumpolyoxyethylene alkyl ether sulfate, benzalconium chloride,alkyltrimethylammonium chloride, benzyltrimethylammonium chloride, nonylphenol ethoxylate, octyl phenyl polyoxyethylene ether, laurylpolyoxyethylene ether, and cetyl polyoxyethylene ether.

(12) The method according to item (1), wherein said sample is awater-based dispersion or an aqueous solution of the carbon nanotubes.

(13) The method according to item (1), wherein said carbon nanotubes aresurface modified with a saturated or unsaturated carbon chain moleculehaving a carboxyl group or an amino group as a substituent in themolecule through a covalent bond, an ionic bond, a hydrogen bond, or anintermolecular interaction.

(14) The method according to item (1), wherein said sample is a solutionfurther containing a metal ion and an electron donor.

(15) The method according to item (14), wherein said solution containsthe metal ion at a concentration of 0.001 to 10%.

(16) The method according to item (14), wherein said solution containsthe electron donor at a concentration of 0.001 to 10%.

(17) The method according to item (14), wherein said electron donor isselected from the group consisting of alcohols, amines, arginine,benzaldehyde, hydrazine, carboxylic acids, amino acids, toluene,alkylbenzenes, terpenes, ethers, silanes, and thiols.

(18) A method for analyzing a carbon nanotube having a desired physicalproperty in a sample, comprising the following steps of:

a) irradiating light to the sample expected to contain the carbonnanotube;

b) selecting the carbon nanotube having the desired physical property;and

c) identifying the selected carbon nanotube.

(19) The method according item (18), wherein said physical propertyincludes at least either a diameter or a chiral vector.

(20) A carbon nanotube separated by the method according to item (2),having uniformity in at least either a diameter or a chiral vector.

(21) A carbon nanotube composition, obtained by the method according toitem (2), wherein the composition has an increased content of the carbonnanotube having uniformity in at least either a diameter or a chiralvector.

(22) A carbon nanotube composition containing a carbon nanotube havinguniformity in at least either a diameter or a chiral vector with greaterthan or equal to 99% purity.

(23) A carbon nanotube thin film obtained by adsorbing and fixing thecarbon nanotube according to item (20) on a support.

(24) A carbon nanotube array obtained by adsorbing and fixing the carbonnanotube according to item (20) arranged in predefined patterns on asupport.

(25) An optical filter comprising the carbon nanotube thin filmaccording to item (23).

(26) An electronic device comprising the carbon nanotube thin filmaccording to item (23).

(27) The electronic device according to item (26), selected from thegroup consisting of a conductive thin film, a dielectric thin film, asensor electrode, an electrode for a high energy density fuel cell, ahighly functional display, a single-molecule detection sensor, anacceleration detection sensor, and a magnetic field detection sensor.

(28) An apparatus for separating, concentrating, or refining a carbonnanotube having a desired physical property in a sample, comprising

A) an introduction part for a sample containing the carbon nanotubes;

B) means for irradiating light to the sample; and

C) means for selecting the carbon nanotube having the desired physicalproperty.

(29) The apparatus according to item (28), wherein said physicalproperty includes at least either a diameter or a chiral vector.

(30) The apparatus according to item (28),

wherein said means B) is a light source of monochromatic light or laserlight having a certain wavelength within a range covering from the nearinfrared region to the ultraviolet region.

(31) The apparatus according to item (28), wherein said means B) is apolychromatic light source within a range covering from the nearinfrared region to the ultraviolet region for depositing a metal on thecarbon nanotube.

(32) The apparatus according to item (28), wherein said means C) is anelectromagnet with controllable magnetism for generating a predeterminedmagnetic field for depositing the carbon nanotube having the desiredphysical property.

(33) The apparatus according to item (28), wherein said means C) ischromatography.

(34) The apparatus according to item (28), wherein said sample is asolution further containing a surfactant.

(35) The apparatus according to item (28), wherein said sample is awater-based dispersion or an aqueous solution of the carbon nanotube.

(36) The apparatus according to item (28), wherein said sample is asolution further containing a metal ion and an electron donor.

EFFECT OF THE INVENTION

The present method and/or apparatus described herein can provide highlyselective separation, concentration or purification of carbon nanotubeshaving a uniform physical property, especially at least either adiameter or a chiral vector, by taking advantage of thestructure-sensitive properties of carbon nanotubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a correlation between an electronic energy level of acarbon nanotube and a redox potential of a metal in the case of (a), ametallic single-walled carbon nanotube.

FIG. 1B shows a correlation between an electronic energy level of acarbon nanotube and a redox potential of a metal in the case of (b), asemiconducting single-walled carbon nanotube.

FIG. 2 shows a reaction mechanism expected between a single-walledcarbon nanotube and a metal ion in the invention.

FIG. 3 shows schematic views of a Raman spectrum detector and a typicalRaman spectrum of a single-walled carbon nanotube.

FIG. 4 shows an atomic force microscopic image of the carbon nanotubesurface in which a metal is deposited.

FIG. 5 shows Raman spectra in Radical Breathing Mode of the carbonnanotube before and after metal deposition in the invention.

FIG. 6 shows the relation between the types of metals used in theinvention and the diameter of a separated carbon nanotube.

FIG. 7 shows the results of Fe ion deposition by excitation at 514 nmexcitation wavelength.

FIG. 8 shows the structural drawing of an apparatus of one embodiment ofthe invention.

FIG. 9 shows the structural drawing of an apparatus of anotherembodiment of the invention.

FIG. 10 shows the structural drawing of an apparatus of further anotherembodiment of the invention.

FIG. 11 shows the structural drawing of an apparatus of an even furtheranother embodiment of the invention.

BEST MODES OF THE EMBODIMENTS OF THE INVENTION

Hereinafter, the present invention will be described. It should beunderstood that, throughout the specification, expressions in singularforms also include concepts of plural forms unless otherwise stated.Furthermore, it should be understood that the terms as used herein havethe meanings which are generally referred to in the field, unlessotherwise stated.

Terms

Hereinafter, definitions of the terms used herein will be listed.

As used herein, “carbon nanotube (Carbon NanoTube, abbreviation: CNT)”refers to a type of carbon cluster represented as C_(n) (n is aninteger, indicting number of carbon atoms), which is a structurecomprising a single layer or multiple layers of graphite rolled up toform a cylindrical shape. The structure of the carbon nanotube isdefined in accordance with the physical properties such as diameter,chiral vector thereof and the like, wherein the chiral vector defines adegree of twist, and the way of winding such as rightward-winding,leftward-winding and the like. The representative examples of thestructures include, but are not limited to, (5,5) armchair type, (9,0)zigzag type, (9, 1) chiral type, and the like. The “carbon nanotube”according to the invention may be a “single-walled carbon nanotube(abbreviation: SWNT)”, which comprises a one-atom-thick layer ofgraphite, or a “multi-walled carbon nanotube (abbreviation: MWNT)”,which comprises multiple layers of graphite rolled in on themselves toform a tube shape.

The “carbon nanotube” of the invention may also be a pure carbonnanotube or a carbon nanotube substituted with any proper substituentfor enabling solvation of the carbon nanotube to a water-based ororganic solvent. In one preferable embodiment, the “carbon nanotube” ofthe invention may be surface-modified with a saturated or unsaturatedcarbon chain molecule having a carboxyl group or an amino group as asubstituent in the molecule through a covalent bond, an ionic bond, ahydrogen bond, or intermolecular interaction.

The “carbon nanotube” of the invention can be produced by the followingthree conventional methods.

A) Arc Discharge Method

The arc discharge method is a method employed for manufacturing a carbonnanotube in the early period. Two graphite rod electrodes are arrangedas closely as several nanometers to each other, and then applied, in anatmosphere of an inert gas, with high voltage provided by the DC powersource connected to the electrodes so as to volatilize the graphite rodsthrough the resultant high intensity discharge between the cathode andanode, thereby forming carbon clusters. Cooling of the obtained carbonclusters up to room temperature deposits them on the cathode in variousforms such as carbon nanotube, fullerene and the like. While onlymulti-walled carbon nanotubes may form in the absence of a catalyst,single-walled carbon nanotubes may form in the presence of some metalcatalysts such as Co, Ni or Fe.

B) Laser Evaporation Method

Similar to the above-mentioned method, graphite rods are used in themethod. Specifically, for example, Nd/YAG laser irradiation evaporatesgraphite rods with argon gas which flows slowly at 500 Torri in anelectric furnace, heading up to approximately 1200, thereby formingSWNTs. The method allows for a large-scale production of SWNTs.

C) Chemical Vapor Deposition Method (CVD Method)

In this CVD method, for example, the substrate is exposed to volatileprecursors such as methane, which at high temperature (e.g., 600° C.)can be a source of atoms, and decompose on the substrate surface torelease carbon atoms, thereby forming carbon nanotubes thoughconfiguration of bonds. Although the CVD method is more suitable forindustrial mass production as compared with the above-mentioned twomethods, the CVD method is not suitable for production of asingle-walled carbon nanotube.

Carbon nanotubes which are commercially available may be subjected tothe purification and separation process according to the presentinvention.

As used herein, “sample containing carbon nanotube(s)” may include thecarbon nanotubes produced by the above-mentioned three methods, carbonnanotubes which are commercially available, and crude compositions whichare expected to contain carbon nanotubes; as well as organic solutions,aqueous solutions or water-based dispersions containing the crudecompositions. The above mentioned “sample containing carbon nanotube(s)”can further contain impurities such as a surfactant and an electrondonor. In addition to the produced carbon nanotubes, the above-mentionedcrude compositions may contain metals or various carbon impurities.

As used herein, “selecting” or “selection (of)” a carbon nanotube havinga desired physical property, refers to precipitating or concentrating ancarbon nanotube of subject from a crude composition containing orexpected to contain the carbon nanotube. “Selecting” may further includethe step of separating the precipitated or concentrated material.

As used herein, “separating” or “separation (of)” a carbon nanotube witha desired physical property refers to substantially separating from anative environment, where the carbon nanotube exists in a sample beforeseparation, or refining or purifying the carbon nanotube.

As used herein, “purifying”, “purification”, “refining” or “refinement”of a carbon nanotube with a desired physical property refers to removingat least one of components accompanied with the carbon nanotube in thenative environment, where the carbon nanotube exists in a sample.Therefore, the scope intended in a practical form of these termspartially overlaps with the scope of “separation”. Although the state ofthe purified carbon nanotube indicates higher density of the carbonnanotubes than that of the corresponding unpurified state, which meansthe nanotube is in a concentrated state, the concept of “purification”also comprises the state where the carbon nanotubes are notconcentrated, but has at least one of the components which isaccompanied in native state, removed out.

As used herein, “concentrating” or “concentration” of a carbon nanotubewith a desired physical property refers to a process for increasing thecontent of a substance of interest in a sample as compared to thecorresponding content of the substance in the unconsecrated state.Accordingly, the concept of “concentration” overlaps with those of“purification” and/or “separation”. Although the concentrated substance(e.g., a carbon nanotube with a desired physical property) remains in asample with a decreased content of an impurity as compared to that ofthe impurity in an unconcentrated state, there may be an increasedcontent of another certain impurity in the concentrated state,indicating that the concept of “concentrated” state comprises a statewhich is not “purified”.

As used herein, “identifying” or “identification” refers todetermination of characteristics of a subject substance. There arevarious measuring methods for identification, which include, but notlimited to, physical analysis methods such as Raman spectroscopy.

As used herein, “physical property” or “physical properties” refers to aphysical character of carbon nanotube, including, for example, diameter,chiral vector, length and the like.

As used herein, “single-walled structure” refers to a structurecomprising a single layer of graphite rolled up to form a cylindricalshape of a carbon nanotube. Raman spectroscopy can estimate whether ornot a carbon nanotube has a single-walled structure. The resonance Ramaneffects in the case of SWNT allows detection of single isolated tubes. Astrong signal can be observed in a region of which Raman shift is equalto or less than 400 cm⁻¹ of the Raman spectrum, wherein the region iscalled radial breathing mode. The frequency of the radial breathing modeis commonly known as being proportional to the inverse of the nanotubediameter. Therefore, by performing Raman spectrum measurement, it ispossible to confirm the existence of the single-walled carbon nanotubeand to determine the diameter of the carbon nanotube. In addition, inthe case of the multi-walled carbon nanotube, it is known that althoughthe observation of MWNT with a transmission electron microscope (TEM)can confirm its tube-like shape, the signal is very weak in the radialbreathing mode in the Raman spectrum measurement.

As used herein, “magnetic field” refers to a field being in a physicalstate on which a magnetic force works. The field can be found in thevicinity of a magnet or a medium in which electric current flows. Asused herein, means for providing the magnetic field in the inventionincludes, but not limited to, a permanent magnet or an electromagnetwhich can control magnetism.

As used herein, “chromatography” refers to one of the methods forseparating a specific targeted substance or substance group in a sampleof a mixture from other substances which coexist in the sample, whereinthe method involves utilizing the difference in mobility (equilibriumdistribution) among the substances which travel in a carrier (stationaryphase). Therefore, any technique which can separate a targeted substancein a sample form other components of the sample, falls within the scopeof “chromatography”. The chromatography may be employed for separating adesired substance from a mixture or for qualitatively or quantitativelyanalyzing the desired substance. For example, as used herein, anelectrophoresis technique, which is usually not called chromatography,falls within the scope of the chromatography, since the electrophoresistechnique can separate at least one components in a sample of a mixturefrom the other components of the sample. The stationary phase isgenerally a liquid or a solid. The mobile phase is generally a liquid ora gas. By adsorbing a sample on one of the ends of a stationary phasesuch as an adsorbent or a mobile phase; and running a proper solvent,which comprises the mobile phase together with the sample, on or throughthe stationary phase, the components in the sample travels through thestationary phase while repeatedly making adsorption with, or elutionfrom, a certain portion of the stationary phase such as the surface orthe inside of the stationary phase. During the travel of the components,the difference in mobility among the components allows for theseparation of the mixture, wherein the mobility of respective componentsreflects the degree of preference in adsorbing with the stationaryphase. The technique which uses a liquid as the mobile phase, is calledliquid chromatography. Conventionally, depending on whether the mobilephase is a liquid or a gas, the chromatography is classified into liquidchromatography (LLC and LSC, HPLC and FPLC (trade name)) and gaschromatography (e.g. GLC, GSC). Also, the separation mechanismcategorizes chromatography techniques, for example, as chiralchromatography, adsorption chromatography, distribution chromatography,ion exchange chromatography, hydrophobic chromatography, size-excludingchromatography (gel chromatography such as gel permeation chromatography(GPC) and gel filtration chromatography (GFC)), salting-outchromatography, reversed phase chromatography, affinity chromatography,supercritical fluid chromatography, high performance counter flowdistribution chromatography, and perfusion chromatography. Also,depending on the form of the solid phase, chromatography can beclassified into, for example, column chromatography, thin layerchromatography (e.g. paper chromatography) and the like. The method ofthe invention can employ any type of the above mentioned chromatographictechniques.

As used herein, “electron donor” refers to a compound which donateselectrons to the occupied energy level of the carbon nanotube which haveloose electrons. Examples of the electron donor of the inventioninclude, but are not limited to, alcohols, amines, arginine,benzaldehyde, hydrazine, carboxylic acids, amino acids, toluene,alkylbenzenes, terpenes, ethers, silanes, and thiols. These exemplaryelectron donors are as defined below. A preferable donor in theinvention is methanol.

As used herein, “support” and “substrate” are interchangeably usedunless otherwise specified, and refer to a material which is preferablya solid, and is capable of supporting another substance in the presenceof a fluid (particularly, a solvent such as a liquid). The material forthe support may include, but are not limited to, any solid materialswhich have a property to be bonded with a substance of the invention bya covalent bond or a non-covalent bond or have been modified into aderivative so as to have such a property. The support may be maintained,more preferably, in a solid state under conditions for purification,concentration, separation, or analysis. The material to be used as thesupport may be any material which can form solid surfaces, including,but not limited to, for example, glass (e.g., slide glass), silica,silicon, ceramics, silicon dioxide, plastics, metals (including alloys),natural and synthetic polymers (e.g., polystyrene, cellulose, chitosan,dextran, and nylon). The support may be composed of multiple layers ofdifferent materials. For example, as the support, there are used aplurality of inorganic insulating materials, including, for example, butnot limited to glass, quartz glass, alumina, sapphire, forsterite,silicon carbide, silicon oxide, silicon nitride, and the like. Further,examples of the material used as the support may include, but are notlimited to, organic materials such as polyethylene, ethylene,polypropylene, polyisobutylene, polyethylene terephthalate, unsaturatedpolyester, fluorine-containing resin, polyvinyl chloride, polyvinylidenechloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal,acrylic resin, polyacrylonitrile, polystyrene, acetal resin,polycarbonate, polyamide, phenol resin, urea resin, epoxy resin,melamine resin, styrene-acrylonitrile copolymer,acrylonitrile-butadiene-styrene copolymer, silicone resin, polyphenyleneoxide, polysulfone and the like. Films used for blotting such as a nylonfilm, a nitrocellulose film, a PVDE film and the like can also be usedin the present invention. In the case that a nylon film is used, theresults can be analyzed using a simple analysis system. In the case ofanalysis of a specimen with a high density, it is preferable to use aharder material such as glass.

As used herein for carbon nanotubes in the present invention,“adsorption/fixation” refers to physical or chemical adsorption on a“support” or “substrate”. For the physical adsorption, a technique maybe employed for spreading carbon nanotubes on a plane to form a film.The morphology of the film formed by spreading into a plane may include,for example, but are not limited to, a cast film, a monomolecular film,and a self-adsorption monomolecular film. As used herein, “cast film”refers to a film formed by casting method and such a cast film can beproduced by casting a solution containing a material of the carbonnanotube and drying the cast solution. As used herein, “monomolecularfilm” refers to a film comprising a monomolecular layer of a thicknessof nanometer order, formed at a gas-liquid interface or a solid-liquidinterface. The invention will utilize a technique of transferring amonomolecular film containing the carbon nanotube of the invention ontoa support. In the invention, it is preferable to employ aLangmuir-Blodgett film (so-called, LB film) among the “monomolecularfilm” as defined in a board sense, which are obtained through depositionfrom the surface of a solution containing a monolayer of the inventivecarbon nanotubes onto a solid substrate by any method for transferringthe monolayer onto the substrate. The most common methods for assemblinga monomolecular film include, but are not limited to, a technique fordipping a solid support (or solid substrate) vertically, up and down ina monomolecular film on the surface of liquid under a controlledconstant surface pressure. Another method for assembling monomolecularfilm includes a horizontal-lifting method, which can transfer only asingle layer of monomolecular film onto a solid support. Thehorizontal-lifting method is a useful technique for the presentinvention.

As used herein, “accumulate” or “accumulation” refers to transferring amonomolecular film to a solid support, and the number of times oftransferring the monomolecular film to the solid support may be one ormore times. In order to accumulate monomolecular films on the solidsupport in the state where the films can retain their structure andorganization as film, those skilled in the art can take various measuresto produce the film while kept in the above state, but are required, atleast, to spread the inventive carbon nanotubes on the surface of aliquid, thereby forming monomolecular films. Carbon nanotubes whichconsist of pure carbon can float in the water due to the hydrophobicproperty, and the carbon nanotubes may be used with or withoutsubstitution with hydrophilic functional group, wherein the hydrophilicfunctional group can render an amphiphilic property to the carbonnanotubes. As used herein, “self-adsorbing monomolecular film” refers toa monomolecular layer obtained by spontaneous chemical adsorption of thecarbon nanotube molecule through a disulfide or dithiol on an evaporatedmetal substrate, such as an evaporated gold substrate.

As used herein, “introducing” or “introduction (of)” a sample refers totransferring a sample to a place where the reaction according to theinvention will occur. A sample introduction part may have any shape aslong as the shape is suitable for introducing a sample. Also, an exampleof methods for introducing a sample includes, but is not limited to, aninjector method, an on-column method, a method of flowing the injectedsample into a column by a mobile phase, a sample valve method and like.Means for introducing the sample may include, but not limited to, asample injector, an auto-sampler, a micro-feeder and the like.

THEORY OF THE INVENTION

The theory of the invention is directed to a selective separation ofcarbon nanotubes for respective physical properties by taking advantageof the electronic energy level of a carbon nanotube and a redoxpotential of a metal. Here, the correlation between them is illustratedin FIG. 1.

A possible reaction mechanism between a carbon nanotube and a metal ion,expected in view of the above correlation, is illustrated in FIG. 2.That is, FIG. 2 shows a possible reaction mechanism of Fe²⁺ and a carbonnanotube, at an electronic energy level. For a detailed description ofthe mechanism, firstly, light irradiation will induce an electrontransition in a carbon nanotube from an occupied level to a non-occupiedlevel of the carbon nanotube, across the band gap of the tube, of whichthe magnitude corresponds to the excitation light energy. Then, theexcited electron is transferred down to an energy level of a metal ionsuch as Fe²⁺, since the non-occupied level is closer to the redoxpotential of the metal ion (in this case, Fe²⁺) than the occupied levelof the carbon nanotube. Consequently, Fe²⁺ is converted into Fe anddeposited on the carbon nanotube. The electron which has been lost fromthe occupied energy level of the carbon nanotube is compensated bysupplying an electron to the occupied energy level of the carbonnanotube from methanol as an electron donor. That is the outline of thereaction mechanism expected in the invention.

Raman Spectroscopy of Carbon Nanotube

One embodiment of the invention is directed to a method of collectingcarbon nanotubes which have uniformities in at least either of adiameter or a chiral vector, by reductive deposition of a metal on thecarbon nanotubes through photocatalytic reaction, followed byapplication of a magnetic field so as to attract the deposited metal.The gathering behavior of the carbon nanotubes can be observed in aRaman spectrum.

A Raman spectrum detector and a schematic drawing of a typical Ramanspectrum of the carbon nanotube are shown in FIG. 3. The Raman spectrumof the carbon nanotube generally contains four kinds of modes (that is,RBM (Radial Breathing Mode), D-band, G-band, and G′-band). In theinvention, by taking particular note of the RBM peak which depends onthe diameter of the carbon nanotubes, the gathering behavior andselectivity of the carbon nanotube have been investigated.

Organic Chemistry

Organic chemistry is described in, for example, Organic Chemistry, R. T.Morrison, R. N. Boyd 5th ed. (1987) and the like, relevant portions ofwhich are incorporated herein as a reference.

In this specification, unless otherwise specified, “substitution” meanssubstitution of one or two or more hydrogen atoms in an organic compoundor a substituent with another atom or an atomic group. It is possiblethat one hydrogen atom is removed and substituted with a monovalentsubstituent, and also that two hydrogen atoms are removed andsubstituted with a divalent substituent.

In the case that the carbon nanotube of the invention is substitutedwith a substituent R, one or a plurality of R groups exist and in thecase that a plurality of R groups exist, the respective groups may beindependently selected from the group consisting of hydrogen, alkyl,substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,substituted alkenyl, cycloalkenyl, substituted cycloalkenyl, alkinyl,substituted alkinyl, alkoxy, substituted alkoxy, carbocyclic group,substituted carbocyclic group, heterocyclic group, substitutedheterocyclic group, halogen, hydroxy, substituted hydroxy, thiol,substituted thiol, cyano, nitro, amino, substituted amino, carboxy,substituted carboxy, acyl, substituted acyl, thiocarboxy, substitutedthiocarboxy, amido, substituted amido, substituted carbonyl, substitutedthiocarbonyl, substituted sulfonyl, and substituted sulfinyl.

The substituent R for making the carbon nanotube of the inventionsoluble in a water-based solvent is preferably polar groups such ascarboxyl group (or carboxy group) or amino group or saturated orunsaturated carbon chains having a polar group such as carboxyl group oramino group in the molecule. On the other hand, as the substituent R formaking the carbon nanotube of the invention soluble in an organicsolvent, those which are hydrophobic are preferable and examples includeC1-C6 alkyl, C1-C5 alkyl, C1-C4 alkyl, C1-C3 alkyl, and C1-C2 alkyl.

As used herein, “heterocyclic (group)” refers to groups having cyclicstructure containing carbon atoms as well as hetero atoms. The heteroatoms may be selected from the group consisting of O, S, and N and theymay be same or different and one or more hetero atoms may be included.The heterocyclic group may be aromatic or non-aromatic and alsomonocyclic or polycyclic. The heterocyclic group may be substituted.

As used herein, “carbon chain” refers to alkyl, substituted alkyl,cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl,cycloalkenyl, and substituted cycloalkenyl.

As used herein, “alkyl” refers to a monovalent group generated when onehydrogen atom is lost from aliphatic hydrocarbon (alkane) such asmethane, ethane, propane, and the like, and is represented byC_(n)H_(2n+1)— in general (herein, n is a positive integer). Alkyl maybe a straight chain or a branched chain. As used herein, “substitutedalkyl” refers to an alkyl having the Hydrogen atom (H) of an alkylsubstituted by a substituent as defined below. Specific examples of suchalkyls may be, C1-C2 alkyl, C1-C3 alkyl, C1-C4 alkyl, C1-C5 alkyl, C1-C6alkyl, C1-C7 alkyl, C1-C8 alkyl, C1-C9 alkyl, C1-C10 alkyl, C1-C11 alkylor C1-C12 alkyl, C1-C2 substituted alkyl, C1-C3 substituted alkyl, C1-C4substituted alkyl, C1-C5 substituted alkyl, C1-C6 substituted alkyl,C1-C7 substituted alkyl, C1-C8 substituted alkyl, C1-C9 substitutedalkyl, C1-C10 substituted alkyl, C1-C11 substituted alkyl, or C1-C12substituted alkyl. Herein, for example, C1-C10 alkyl denotes straightchain or branched alkyl having 1-10 carbon atoms, and examples may bemethyl(CH₃—), ethyl(C₂H₅—), n-propyl (CH₃CH₂CH₂—), isopropyl((CH₃)₂CH—), n-butyl (CH₃CH₂CH₂CH₂—), n-pentyl (CH₃CH₂CH₂CH₂CH₂—),n-hexyl (CH₃CH₂CH₂CH₂CH₂CH₂—), n-heptyl (CH₃CH₂CH₂CH₂CH₂CH₂CH₂—),n-octyl (CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂—), n-nonyl(CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—), n-decyl(CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—), —C(CH₃)₂CH₂CH₂CH(CH₃)₂, —CH₂CH(CH₃)₂and the like. Further, for example, C1-C10 substituted alkyl refers toC1-C10 alkyl having one or more hydrogen atoms substituted bysubstituents.

As used herein, “lower alkyl” refers to C1-C6 alkyl and preferably C1alkyl or C2 alkyl.

As used herein, “cycloalkyl” refers to an alkyl having a cyclicstructure. The term “substituted cycloalkyl” refers to a cycloalkylhaving the H of the cycloalkyl substituted by a substituent definedbelow. Specific examples of cycloalkyls may be C3-C4 cycloalkyl, C3-C5cycloalkyl, C3-C6 cycloalkyl, C3-C7 cycloalkyl, C3-C8 cycloalkyl, C3-C9cycloalkyl, C3-C10 cycloalkyl, C3-C11 cycloalkyl, C3-C12 cycloalkyl,C3-C4 substituted cycloalkyl, C3-C5 substituted cycloalkyl, C3-C6substituted cycloalkyl, C3-C7 substituted cycloalkyl, C3-C8 substitutedcycloalkyl, C3-C9 substituted cycloalkyl, C3-C10 substituted cycloalkyl,C3-C11 substituted cycloalkyl or C3-C12 substituted cycloalkyl. Forexample, cycloalkyl may be cyclopropyl, cyclohexyl, or the like.

As used herein, “alkenyl” refers to a monovalent group generated whenone hydrogen atom is lost from an aliphatic hydrocarbon having onedouble bond in a molecule, such as ethylene and propylene, and, ingeneral, is represented by C_(n)H_(2n−1)— (herein, n is a positiveinteger of 2 or higher). The term “substituted alkenyl” refers to analkenyl having the H of the alkenyl substituted by a substituent asdefined below. Specific examples of alkenyls may be C2-C3 alkenyl, C2-C4alkenyl, C2-C5 alkenyl, C2-C6 alkenyl, C2-C7 alkenyl, C2-C8 alkenyl,C2-C9 alkenyl, C2-C10 alkenyl, C2-C11 alkenyl or C2-C12 alkenyl, C2-C3substituted alkenyl, C2-C4 substituted alkenyl, C2-C5 substitutedalkenyl, C2-C6 substituted alkenyl, C2-C7 substituted alkenyl, C2-C8substituted alkenyl, C2-C9 substituted alkenyl, C2-C10 substitutedalkenyl, C2-C11 substituted alkenyl or C2-C12 substituted alkenyl.Herein, for example, C2-C10 alkenyl refers to a straight chain orbranched alkenyl including 2-10 carbon atoms, and examples of alkenylsinclude vinyl (CH₂═CH—), allyl (CH₂═CHCH₂—), CH₃CH═CH— and the like.Further, for example, C2-C10 substituted alkenyl refers to C2-C10alkenyl which has 1 or more hydrogen atoms substituted by substituents.

As used herein, “cycloalkenyl” refers to an alkenyl having a cyclicstructure. The term “substituted cycloalkenyl” refers to a cycloalkenylhaving the H of a cycloalkenyl substituted by a substituent as definedbelow. Specific examples of cycloalkenyl may be C3-C4 cycloalkenyl,C3-C5 cycloalkenyl, C3-C6 cycloalkenyl, C3-C7 cycloalkenyl, C3-C8cycloalkenyl, C3-C9 cycloalkenyl, C3-C10 cycloalkenyl, C3-C11cycloalkenyl, C3-C12 cycloalkenyl, C3-C4 substituted cycloalkenyl, C3-C5substituted cycloalkenyl, C3-C6 substituted cycloalkenyl, C3-C7substituted cycloalkenyl, C3-C8 substituted cycloalkenyl, C3-C9substituted cycloalkenyl, C3-C10 substituted cycloalkenyl, C3-C11substituted cycloalkenyl or C3-C12 substituted cycloalkenyl. Forexample, preferable examples of cycloalkenyl include 1-cyclopentenyl,2-cyclohexenyl or the like.

As used herein, “alkynyl” refers to a monovalent group generated whenone hydrogen atom is lost from an aliphatic hydrocarbon having onetriple bond in a molecule, such as acetylene, and, in general, isrepresented by C_(n)H_(2n−3)— (herein, n is a positive integer of 2 orhigher). The term “substituted alkynyl” refers to alkynyl having the Hof the alkynyl substituted by a substituent as defined below. Specificexamples of alkynyls may be C2-C3 alkynyl, C2-C4 alkynyl, C2-C5 alkynyl,C2-C6 alkynyl, C2-C7 alkynyl, C2-C8 alkynyl, C2-C9 alkynyl, C2-C10alkynyl, C2-C11 alkynyl, C2-C12 alkynyl, C2-C3 substituted alkynyl,C2-C4 substituted alkynyl, C2-C5 substituted alkynyl, C2-C6 substitutedalkynyl, C2-C7 substituted alkynyl, C2-C8 substituted alkynyl, C2-C9substituted alkynyl, C2-C10 substituted alkynyl, C2-C11 substitutedalkynyl or C2-C12 substituted alkynyl. Herein, for example, C2-C10alkynyl refers to, for example, a straight chain or branched alkynylincluding 2-10 carbon atoms, and examples of alkynyl may be ethynyl(CH≡C—), 1-propynyl (CH₃C≡C—) or the like. Further, for example, C2-C10substituted alkynyl refers to C2-C10 alkynyl having 1 or more hydrogenatoms substituted by substituents.

As used herein, “alkoxy” refers to a monovalent group generated when ahydrogen atom of a hydroxy group of an alcohol is lost, and in general,is represented by C_(n)H_(2n+1)O— (herein, n is an integer of one orhigher). The term “substituted alkoxy” refers to alkoxy having H of thealkoxy substituted by a substituent as defined below. Specific examplesof alkoxys may be C1-C2 alkoxy, C1-C3 alkoxy, C1-C4 alkoxy, C1-C5alkoxy, C1-C6 alkoxy, C1-C7 alkoxy, C1-C8 alkoxy, C1-C9 alkoxy, C1-C10alkoxy, C1-C11 alkoxy, C1-C12 alkoxy, C1-C2 substituted alkoxy, C1-C3substituted alkoxy, C1-C4 substituted alkoxy, C1-C5 substituted alkoxy,C1-C6 substituted alkoxy, C1-C7 substituted alkoxy, C1-C8 substitutedalkoxy, C1-C9 substituted alkoxy, C1-C10 substituted alkoxy, C1-C11substituted alkoxy or C1-C12 substituted alkoxy. Herein, for example,C1-C10 alkoxy refers to a straight chain or branched alkoxy including1-10 carbon atoms, and examples of alkoxys may be methoxy (CH₃O—),ethoxy (C₂H₅O—), n-propoxy (CH₃CH₂CH₂O—), and the like.

As used herein, “carbocyclic group” refers to a group which includes acyclic structure including only carbons, and which is a group other thanthe above-mentioned “cycloalkyl”, “substituted cycloalkyl”,“cycloalkenyl”, and “substituted cycloalkenyl”. A carbocyclic group maybe aromatic or nonaromatic, and may be monocyclic or polycyclic. Theterm “substituted carbocyclic group” refers to a carbocyclic grouphaving the H of the carbocyclic group substituted by a substituent asdefined below. Specific examples of carbocyclic groups may be C3-C4carbocyclic group, C3-C5 carbocyclic group, C3-C6 carbocyclic group,C3-C7 carbocyclic group, C3-C8 carbocyclic group, C3-C9 carbocyclicgroup, C3-C10 carbocyclic group, C3-C11 carbocyclic group, C3-C12carbocyclic group, C3-C4 substituted carbocyclic group, C3-C5substituted carbocyclic group, C3-C6 substituted carbocyclic group,C3-C7 substituted carbocyclic group, C3-C8 substituted carbocyclicgroup, C3-C9 substituted carbocyclic group, C3-C10 substitutedcarbocyclic group, C3-C11 substituted carbocyclic group, or C3-C12substituted carbocyclic group. The carbocyclic group may also be C4-C7carbocyclic group or C4-C7 substituted carbocyclic group. The examplesof carbocyclic group may be a phenyl group having one hydrogen atomdeleted. The deletion site of the hydrogen may be any site which ischemically possible, and it may be on an aromatic ring or on anonaromatic ring.

As used herein, “heterocyclic group” refers to a group having a cyclicstructure including carbon and hetero atoms. Herein, hetero atoms may beselected from a group consisting of O, S and N, may be the same ordifferent from each other, and one or more heteroatoms may be included.A heterocyclic group may be aromatic or nonaromatic, and may bemonocyclic or polycyclic. The term “substituted heterocyclic group”refers to a heterocyclic group having the H of the heterocyclic groupsubstituted by a substituent as defined below. Specific examples ofheterocyclic group may be C3-C4 carbocyclic group, C3-C5 carbocyclicgroup, C3-C6 carbocyclic group, C3-C7 carbocyclic group, C3-C8carbocyclic group, C3-C9 carbocyclic group, C3-C10 carbocyclic group,C3-C11 carbocyclic group, C3-C12 carbocyclic group, C3-C4 substitutedcarbocyclic group, C3-C5 substituted carbocyclic group, C3-C6substituted carbocyclic group, C3-C7 substituted carbocyclic group,C3-C8 substituted carbocyclic group, C3-C9 substituted carbocyclicgroup, C3-C10 substituted carbocyclic group, C3-C11 substitutedcarbocyclic group, or C3-C12 substituted carbocyclic group, which hasone or more carbon atoms substituted by hetero atoms. The heterocyclicgroup may also be a C4-C7 carbocyclic group or C4-C7 substitutedcarbocyclic group, which has one or more carbon atoms substituted withhetero atoms. The examples of heterocyclic groups may be a thienylgroup, pyrrolyl group, furyl group, imidazolyl group, pyridyl group, orthe like. The deletion site of the hydrogen may be any site which ischemically possible, and it may be on an aromatic ring or on anonaromatic ring.

As used herein, “phenyl group” refers to a C6 aromatic carbocyclic groupand is a functional group lacking one H from benzene. “Substitutedphenyl group” refers to a group in which H in a phenyl group issubstituted with a substituent as defined below.

As used herein, carbocyclic group or heterocyclic group may besubstituted by a bivalent substituent in addition to being able to besubstituted by a monovalent substituent as defined below. Such abivalent substitution may be oxo substitution (═O) or thioxosubstitution (═S).

As used herein, “halogen” refers to a monovalent group of elements suchas fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and the likewhich belong to group 7B of the periodic table.

As used herein, “hydroxy” refers to a group represented by —OH. The term“substituted hydroxy” refers to hydroxy having the H of the hydroxysubstituted by a substituent as defined below.

As used herein, “cyano” refers to a group represented by —CN, and“nitro” refers to a group represented by —NO₂. The term “amino” refersto a group represented by —NH₂. The term “substituted amino” refers toamino having an H substituted by a substituent defined below.

As used herein, “carboxy” refers to a group represented by —COOH. Theterm “substituted carboxy” is carboxy having an H substituted by asubstituent as defined below.

As used herein, “thiocarboxy” refers to a group having an oxygen atom ofcarboxy group substituted with a sulfur atom, and can be represented by—C(═S)OH, —C(═O)SH or —CSSH. The term “substituted thiocarboxy” isthiocarboxy having the H substituted by a substituent as defined below.

As used herein, “acyl” refers to alkylcarbonyl containing the “alkyl”bound to carbonyl, cycloalkylcarbonyl containing the “cycloalkyl” boundto carbonyl, and arylcarbonyl containing the “aryl” bound to carbonyl.“Acyl” refers to, for example, acetyl, n-propanoyl, i-propanoyl,n-butyloyl, t-butyloyl, cyclopropanoyl, cyclobutanoyl, cyclopentanoyl,cyclohexanoyl, benzoyl, α-naphthoyl, and β-naphthoyl. “Substituted acyl”refers to acyl having hydrogen substituted with a substituent as definedbelow.

As used herein, “amido” refers to a group having a hydrogen of ammoniasubstituted with an acid group (acyl group), and, preferably,represented by —CONH₂. The term “substituted amido” refers to amidowhich is substituted.

As used herein, “carbonyl” refers to a generic term for a substanceincluding —(C═O)—, which is a characteristic group of aldehydes andketones. The term “substituted carbonyl” refers to a carbonyl groupsubstituted by a substituent selected as described below.

As used herein, “thiocarbonyl” refers to a group having the oxygen atomof carbonyl substituted by a sulfur atom, and includes a characteristicgroup —(C═S)—. The thiocarbonyl includes thioketone and thioaldehyde.The term “substituted thiocarbonyl” refers to a thiocarbonyl substitutedby a substituent selected as described below.

As used herein, “sulfonyl” is a generic term for a substance including acharacteristic group, —SO₂—. The term “substituted sulfonyl” refers to asulfonyl substituted by a substituent selected as described below.

As used herein, “sulfinyl” is a generic term for a substance including acharacteristic group, —SO—. The term “substituted sulfinyl” refers to asulfinyl substituted by a substituent selected as described below.

As used herein, “aryl” refers to a group generated when one hydrogenatom linked to a ring of aromatic hydrocarbons is eliminated, andincluded in a carbocyclic group in the present specification. Examplesthereof include phenyl, α-naphthyl, β-naphthyl, anthyl, indenyl,phenanthryl and the like. “Substituted aryl” refers to an arylsubstituted with a substituent selected as described below.

As used herein, “heteroaryl” refers to a group generated when onehydrogen atom linked to a ring of aromatic hydrocarbons having heteroatoms is eliminated, and included in a “heterocyclic group” in thepresent specification. Examples thereof include furanyl, thiophenyl,pyridyl and the like. “Substituted heteroaryl” refers to a heteroarylsubstituted with a substituent selected as described below.

As used herein, “ester” refers to a generic term for a substanceincluding —COO—, which is a characteristic group. The term “substitutedester” refers to ester substituted with a substituent selected asdescribe below.

As used herein, “hydroxyl group” refers to a group represented by —OH.“Hydroxyl group” is interchangeable with “hydroxyl group”.

As used herein, “alcohol” refers to an organic compound having one ormore hydrogen atoms of an aliphatic hydrocarbon substituted by ahydroxyl group and may be used interchangeably with “alcoholderivative”. It is also represented as ROH in the present specification.Herein, R is an alkyl group. Preferably, R may be C1-C6 alkyl. Alcoholmay be, for example, methanol, ethanol, 1-propanol, 2-propanol and thelike, but is not limited to these.

As used herein, “aldehyde” refers to a generic term for a substanceincluding —CHO, which is a characteristic group. “Substituted aldehyde”refers to an aldehyde substituted with a substituent selected asdescribed below, and may be used interchangeably with “aldehydederivative”.

As used herein, “amine” is a general name for compounds obtained bysubstituting hydrogen atom of ammonia NH₃ with a hydrocarbon group andclassified into a primary amine, a secondary amine, and a tertiary aminedepending on the number of the hydrocarbon groups. The term “amine” inthis specification is used interchangeably with “amines”.

As used herein, “carboxylic acid” refers to a generic term for asubstance including —COOH, which is a characteristic group, and areinterchangeable with “carboxylic acid”. “Substituted carboxylic acid”refers to a carboxylic acid substituted with a substituent selected asdescribed below, and may be used interchangeably with “aldehydederivative”.

As used herein, “amino acid” may be a natural or non-natural amino acid.“Amino acid derivative” or “amino acid analogue” refers to those whichare different from naturally occurring amino acids but have the samefunctions as those of the original amino acids. Such amino acidderivatives and amino acid analogous are well known in the art. The term“natural amino acid” or “naturally occurring amino acid” refers to theL-isomer of a natural amino acid. Examples of the natural amino acidinclude glycine, alanine, valine, leucine, isoleucine, serine,methionine, theronine, phenylalanine, tyrosine, tryptophane, cysteine,proline, histidine, aspartic acid, asparagine, glutamic acid, glutamine,y-carboxyglutamic acid, arginine, ornithine, and lysine. As used herein,unless otherwise specified, all amino acids are L-stereoisomer, howevera embodiment using D-amino acid is also included in the invention. Theterm “non-natural amino acid” or “non-naturally occurring amino acid”refers to an amino acid which generally can not be found in a protein.Examples of the non-natural amino acid include D-isomers and L-isomersof norleucine, p-nitrophenylalanine, homophenylalanine,p-fluorophenylalanine, 3-amino-2-benzylepropionic acid, and homoarginineand D-phenylalanine. “Amino acid analogue” refers to a molecule which isnot an amino acid but has an analogous physical property and/or functionto an amino acid. Examples of the amino acid analogue include ethionine,canavanine, and 2-methylglutamine. Amino acid mimetics refer tocompounds which have different chemical structures from amino acids butrender functions in the same manner as naturally occurring amino acids.As used herein, “amino acid” may be protected with a protecting group.

As used herein, “alkylbenzene” refers to an alkyl derivative of benzene,that is, an aromatic hydrocarbon in which an alkyl group is bonded tothe benzene nucleus and the term is used interchangeably with the term“alkylbenzenes” in this specification. The term “alkyl group” is theabove defined “alkyl”.

As used herein, “terpene” refers to a hydrocarbon having a compositionof (C₅H₈)_(n), and this term also includes oxygen-containing compoundswhich are derived from the hydrocarbon and have different degree ofunsaturation from the hydrocarbon. The term “terepene” is usedinterchangeably with the term “terepenes” in this specification.

As used herein, “ether” refer to a compound defined by the generalformula, A-O-A′ wherein a group for A and a group for A′ may be same ordifferent and may independently denote a group selected from alkyl,substituted alkyl, cycloalkyl, substituted cycloalkyl, cycloalkenyl,substituted cycloalkenyl, carbocyclic, substituted carbocyclic and thelike, as defined above. Also, the group for A and the group for A′ maybe bonded to each other to form a cyclic ether. The term “ether” is usedinterchangeably with the term “ethers” in this specification.

As used herein, “silane” is a generic name for silicon hydrides and inaccordance with the number of silicon, there are monosilane, disilane,and trisilane. The term “silane” is used interchangeably with the term“silanes”.

As used herein, “thiol” is a group (mercapto group) obtained bysubstituting oxygen atom of hydroxyl group with sulfur atom, andexpressed as —SH. As used herein, the term “thiol” and “thiols” are usedinterchangeably. “Substituted thiol” refers to a mercapto group of whichhydrogen atom (H) is substituted with the following substituents.

As used herein, C1, C2, . . . Cn indicate the number of carbon atoms.Accordingly, C1 is used for expressing a substituent having one carbonatom.

As used herein, “optical isomer(s)” refers to a pair of compounds or oneof the compounds, whose crystalline or molecular structures are mirrorimages and non-superimposable. It also refers to one of stereoisomers,wherein a set of the optical isomers share the same properties exceptthe optical activity.

As used herein, “substitution” refers to substituting one or two or morehydrogen atom(s) in an organic compound or a substituent with anotheratom or atomic group, if not particularly mentioned. It is possible toremove one hydrogen atom to substitute with a monovalent substituent,and to remove two hydrogen atoms to substitute with bivalentsubstituent.

As used herein, examples of the substituent include, but not limited to,alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkinyl, alkoxy, a carbocyclicgroup, a heterocyclic group, halogen, hydroxy, thiol, cyano, nitro,amino, a carboxy group, carbamoyl, acyl, acylamino, thiocarboxy,substituted amido, substituted carbonyl, substituted thiocarbonyl,substituted sulfonyl, and substituted sulfinyl.

As used herein, “protection reaction” refers to a reaction to add aprotecting group such as t-butoxycarbonyl group to a functional groupwhich is desired to be protected. By protecting a functional group witha protecting group, the reaction of a functional group having highreactivity can be suppressed, and only a functional group having lowerreactivity reacts.

As used herein, “deprotection reaction” refers to a reaction toeliminate a protecting group such as t-butoxycarbonyl. The deprotectionreaction may be a reaction such as a reaction using trifluoroacetic acid(TFA) or a reduction reaction using Pd/C.

In the respective methods of the present invention, intended productsmay be isolated by removing foreign substances (unreacted raw material,by-product, solvent and the like) from a reaction solution using amethod commonly used in the art (for example, extraction, distillation,washing, concentration, precipitation, filtration, drying or the like),and then combining after-treatment methods commonly used in the field ofthe art (for example, adsorption, dissolution, elution, distillation,precipitation, deposition, chromatography, or the like).

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Hereinafter, a preferable embodiment of the invention will be described.

In one aspect, the invention provides a method for separating,concentrating, or refining a carbon nanotube having a desired physicalproperty in a sample, wherein the method comprises steps: a) irradiatinglight to a sample containing a carbon nanotube; and b) selecting thecarbon nanotube having a desired physical property. So far, theconventional methods for producing carbon nanotubes has produced carbonnanotubes which contain various carbon-containing contaminants, and donot have uniformity in diameter and chiral vector. In theabove-mentioned step a), the light is radiated under conditions (e.g.,the light intensity, the distance between a sample and a light source,and the light irradiation time) sufficient to induce the photocatalyticreaction. In the above-mentioned step b), techniques are used forselecting, i.e., collecting or concentrating, a carbon nanotube having adesired physical property, for example, uniformity in at least either adiameter or a chiral vector, from a crude composition containing orexpected to contain a carbon nanotube produced by a conventional methodor a commercially available carbon nanotube or an organic solution, anaqueous solution or a water-based dispersion containing the crudecomposition. The method allows for the highly selective separation andpurification of the carbon nanotubes which have theoretically possible adesired uniformity in at least either a diameter or a chiral vector,from a sample containing carbon nanotubes with a low purity in terms ofthe diameter and/or chiral vector thereof. The present method alsoallows separation of single-walled carbon nanotubes which have a desiredphysical property, that is, still higher uniformity in at least either adiameter or a chiral vector. The light used for the step a) has aspecific wavelength within a range covering from the near infraredregion to the ultraviolet region (typically, from around 300 nm to 4000nm). More preferably, the light is monochromatic light or laser light,which has a specific wavelength within a range covering from the nearinfrared region to the ultraviolet region. Utilization of monochromaticlight or laser light has an advantage in obtaining the narrowerdistribution or the uniformity of at least either a diameter or a chiralvector of the obtained carbon nanotubes.

In a preferable embodiment, the light irradiation in the step a) iscarried out in the presence of a metal. The metal may be a metalcatalyst used during the production of the carbon nanotubes before theseparation. Alternatively, carbon nanotubes in the presence of a metalmay be provided by removal of metals from commercially available carbonnanotubes, followed by addition of a predetermined metal to thenanotubes. Accordingly, light irradiation in the step a) of theabove-mentioned method may selectively induce photocatalytic reactionsand deposition such as electrodeposition of the metal on a targetedcarbon nanotube in the solution. In the above process, selection of theradiated light wavelength and the type of metal to be deposited orelectrodeposited on the excited carbon nanotubes by the irradiation, canallow the selectivity in the diameter and the chiral vector of thecarbon nanotubes, and in the absolute potential at von Hove Singularity(vHs) of the carbon nanotubes. A metal used in the invention may beselected from the group consisting of alkali metals; alkaline earthmetals; transition metals selected from Group IIIA to VIIA elements andGroup IB elements; and rare earth elements. A typical example of themetals used in the invention may include, but not limited to, Fe, Ni,Cu, Ag, Co or Mn. The metal used in the invention can be selectedproperly depending the positional relationship between the redoxpotential of the metal and the electronic energy level of carbonnanotubes (particularly, the single-walled carbon nanotube). Accordingto the invention, in considering that the larger the overlap of energylevels between the redox potential of the metal and the electronicenergy levels of the carbon nanotube in the solution, the more likelythe metal has deposited on the carbon nanotube; a metal which has alarger overlap in energy levels with the desired carbon nanotubes can beselected under the specific distribution of the energy levels in thesolution.

In one preferable embodiment, the selection of the carbon nanotube inthe step b) is carried out by applying a predetermined magnetic field soas to collect the carbon nanotube having a desired physical property(including at least either a diameter or a chiral vector). Applicationof such a magnetic field provides collection or concentration of thecarbon nanotube on which the metal is deposited.

In another preferable embodiment, the selection of the carbon nanotubein the step b) is carried out by a common chromatography technique.

As described, the selection of the carbon nanotube in the step b) may becarried out by application of the magnetic field or chromatographictechnique.

In a further preferred embodiment, in the invention, the method forseparating, concentrating, or purifying the carbon nanotube having adesired physical property (including at least either a diameter or achiral vector) in a sample is carried out using a dispersion or asolution of the carbon nanotube. At the time of producing the dispersionof the carbon nanotubes, a surfactant can be added to the samplecontaining the carbon nanotubes. Exemplary examples of the surfactantused in the invention are selected from, but not limited to, the groupconsisting of sodium dodecyl sulfate, sodium dodecylbenezensulfonate,Triton X (Triton X-100), alkylsulfonaic acid salt, sodiumpolyoxyethylene alkyl ether sulfate, benzalconium chloride,alkyltrimethylammonium chloride, benzyltrimethylammonium chloride, nonylphenol ethoxylate, octyl phenyl polyoxyethylene ether, laurylpolyoxyethylene ether, and cetyl polyoxyethylene ether. Among them,sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and Triton X(Triton X-100) are particularly preferable. The concentration of thesurfactant in the solution may be a concentration which is equal to orhigher than the critical micellar concentration (cmc) of the surfactantused; and may be within a range allowing dispersion of the carbonnanotube as a micelle.

It is known that the carbon nanotubes consisting of pure carbon are notsoluble in any solvent. However, in order to solubilize the carbonnanotubes in an organic or water-based solvent, the carbon nanotubes maybe substituted with a suitable substituent. In order to solubilize thecarbon nanotubes in water, it is preferable to surface-modify the carbonnanotubes of pure carbon with a saturated or unsaturated carbon chainmolecule having a carboxyl group or an amino group as a substituent inthe molecule through a covalent bond, an ionic bond, a hydrogen bond, oran intermolecular interaction.

In another preferable embodiment, in the present invention, a sampleused for a method of separating, concentrating, or purifying the carbonnanotube having a desired physical property (at least either a diameteror a chiral vector) in the sample, is a solution further containing ametal ion and/or an electron donor. The concentration of the metal ionin the solution is preferably 0.001 to 10%, more preferably 0.05 to 5%,and even more preferably 0.1 to 1%. The concentration of the metal ionin the solution is lower than 0.001% is not preferable, because ofinsufficient deposition of the metal on the carbon nanotube surface. Theconcentration over 10% of the ions is not preferable, because it becomesdifficult to carry out purification at the time of removing the metalimpurity from the carbon nanotube thereafter. The concentration of theelectron donor in the solution is preferably equal to or higher thanthat of the metal ion used together. A typical electron donor used inthe invention may be selected from, but not limited to the groupconsisting of alcohols, amines, arginine, benzaldehyde, hydrazine,carboxylic acids, amino acids, toluene, alkylbenzenes, terepenes,ethers, silanes, and thiols. The electron donor in the invention ispreferably alcohols and particularly preferably methanol.

In a preferable embodiment, the invention provides a method of analyzingthe carbon nanotube having a desired physical property in a sample,including a method comprising the steps of a) irradiating light to asample expected to contain the carbon nanotube; b) selecting the carbonnanotube having the desired physical property; and c) identifying theselected carbon nanotube.

The carbon nanotube having a desired physical property (including atleast either a diameter or a chiral vector) is provided by the method ofthe invention described above. Also, a carbon nanotube composition withan increased content of the carbon nanotube having a desired physicalproperty with a desired uniformity (including at least either a diameteror a chiral vector) is provided by the method of the invention describedabove. Further, a carbon nanotube composition containing the carbonnanotube having a high purity (greater than or equal to 99%) and havinguniformity in diameter and chiral vector can be provided. These carbonnanotube compositions can be a carbon nanotube supply source useful forproduction of a carbon nanotube thin film contained in an optical filteror an electron device. A typical example of the electron device mayinclude a conductive thin film, a dielectric thin film, a sensorelectrode, an electrode for a high energy density fuel cell, a highlyfunctional display, a single-molecule detection sensor, an accelerationdetection sensor, and a magnetic field detection sensor.

The carbon nanotube obtained by the method of the invention may beadsorbed/fixed on a support or accumulated on a support to form a carbonnanotube thin film. Also, if the carbon nanotube is adsorbed and fixedin predefined patterns on a support, carbon nanotubes can be obtained inpredefined patterns on a support.

In another aspect, the invention provides an apparatus for separating,concentrating, or purifying a carbon nanotube having a desired physicalproperty in a sample and comprising A) an introduction part for a samplecontaining the carbon nanotube; B) means for irradiating light to thesample; and C) means for selecting the carbon nanotube having thedesired physical property (including at least either a diameter or achiral vector).

In a preferable embodiment, the means B) is a light source ofmonochromatic light or laser light having specific wavelength within arange covering from the near infrared region to the ultraviolet regionso as to deposit a metal on the carbon nanotube. In the invention, asthe means B), a polychromatic light source having certain wavelengthwithin a range covering from the near infrared region to the ultravioletregion so as to deposit a metal on the carbon nanotube may be used (seeFIG. 8).

In another preferable embodiment, the means C) may be an electromagnetwith controllable magnetism for generating a predetermined magneticfield for integrating the carbon nanotube having a desired physicalproperty (including at least either a diameter or a chiral vector) orchromatography.

In another preferable embodiment, the carbon nanotube is continuouslysupplied in the form of a dispersion by flowing a sample containing thecarbon nanotube. Accordingly, the carbon nanotube is depositedselectively as similarly described above, resulting in a two to tentimes increase in the amount of the deposition.

In still another embodiment of the invention, a similar experiment maybe carried out by limiting the light irradiating portion of the lightsource with a lithographic pattern mask (e.g., 10 μm width). As aresult, the carbon nanotube can be space-selectively deposited with thestructure selectivity as similarly described above. Accordingly, thecarbon nanotube having a specific chiral vector can be separated andpurified and fixed at an optional position of a substrate.

In still another further embodiment of the invention, light irradiationis carried out by a near-field probe chip. In this case, the lightirradiation time is controlled to be pulsed light (e.g., 10 ms), so thatone carbon nanotube having a specific chiral vector can bespace-selectively fixed on the substrate surface with the structureselectivity as similarly described above. Accordingly, the carbonnanotube having a specific chiral vector can be fixed on an optionalposition while the number of the carbon nanotube is controlled to be asingle or another optional number.

The reference documents such as scientific documents, patents, andpatent applications cited in this specification are hereby incorporatedby reference in their entirety, as if they were literally described inthis specification.

The above description illustrates preferred embodiments that achieve thefeatures and advantages of the invention; however the invention shouldnot be construed to be limited to the illustrated embodiments. It isunderstood that the scope of the invention should be construed only byclaims. It should be understood that the person skilled in the field canconduct the inventions according to the practically described preferredembodiments of the inventions based on the technical common knowledgeand skills. Also, it should be understood that the reference documentscited in this specification are hereby incorporated by reference intheir entirety, as if they were literally described in thisspecification.

EXAMPLES

Hereinafter, the invention will be described more in detail along withexamples, however it is not intended that the invention be limited tothe illustrated examples.

Example 1 1.1 Metal Deposition on a Carbon Nanotube

Carbon nanotubes (CarboLex AP-Grade SWNT (SWNT: purity 50-70%)) in anaqueous 1% sodium dodecyl sulfate (SDS) solution were subjected toultrasonic dispersion treatment at 24° C. and 12000 rpm for 15 minutesand the supernatant solution was filtered with a syringe filter (0.2 μmpore size filter) and subjected to additional ultrasonic treatment andcentrifugal separation in the same conditions to obtain a micellardispersion.

Next, methanol (Methanol: 99.8% purity, Infinity Pure Grade;commercially available from Wako Pure Chemical Industries, Ltd.) wasadded as an electron donor to the dispersion to a concentration of 0.1%.The following three different metal ion solutions were added to theabove resulting solution to prepare three solutions with different metalions.

I) 0.1 M Fe(NH₄)₂(SO₄)₂ aqueous solution

II) 0.1 M CoCl₂ aqueous solution

III) 0.1 M MnCl₂ aqueous solution

Monochromatic light with an excitation wavelength of 785 nm wassimultaneously radiated under the same conditions to the three solutionsproduced in the above-mentioned manner for excitation. Ions of themetals (Mn, Co, and Fe) in the solutions were respectively reduced anddeposited on the specific carbon nanotubes. The surface of the carbonnanotube on which each metal was deposited, was observed by anatom-field microscope (AFM) (FIG. 4). For the measurement with AFM,NanoScope Multi Mode™ AFM manufactured by Digital Instruments was usedin a tapping mode for the measurement, and NanoScope IIIa was used foranalysis of the results. After each substrate on which the carbonnanotube was collected was carefully washed with ultra pure water(MilliQ water) and dried, the measurement was carried out in atmosphericair. From FIG. 4, it is made clear that each metal was electrodepositedon the surface of the carbon nanotube. The carbon nanotube on which themetal was deposited was collected by using a magnetic field (a magnet).

1.2 Raman Spectroscopy of Carbon Nanotube

The structure of each carbon nanotube collected in the above Section 1.1was evaluated by a microscopic Raman measurement. FIG. 5 shows Ramanspectra of the carbon nanotube before and after the deposition reactionof the metals in radial breaching mode. The spectra show the change ofthe shape having a plurality of peaks within a range of 140 to 270 cm⁻¹to a shape having a main peak of 267 cm⁻¹ by the separation operation.It shows that only a semiconducting carbon nanotube having a diameteraround 0.93 nm and chiral vector (10, 3) was selectively separated andrecovered from the un-purified carbon nanotube sample having a widediameter distribution with a diameter of 0.9 to 1.7 nm. Also, it isfound that the spectra after the separation are changed depending on thedeposited metals and it implies controllability of the separation bychanging the types of metals in this exemplified method. The relation ofthe types of the metals used and the diameter of the separated carbonnanotube is shown in FIG. 6.

FIG. 7 shows the result of the Fe ion deposition by excitation with anexcitation wavelength of 514 nm. The result also shows that only themetallic carbon nanotube with a diameter around 0.90 nm and chiralvector (8, 5) was selectively separated and recovered from anun-purified carbon nanotube sample having a wide diameter distributionwith a diameter of 0.9 to 1.7 nm.

Accordingly, it has been proved that the combination of a selectivelight-induced metal deposition reaction on a carbon nanotube with amagnetic field separation can allow for the high selectivity inpurification of the carbon nanotube having a specific diameter andchirality.

Example 2

FIG. 8 is an apparatus structural drawing showing one embodiment of theinvention. Light with different wavelength values 1064 nm (λ1), 785 nm(λ2), and 514 nm (λ3) were employed as light irradiation sources forphotoelectric chemical metal deposition. A micellar dispersion obtainedby dispersing the carbon nanotube before purification in an aqueous 1%sodium dodecyl sulfate solution was used as the carbonnanotube-containing solution. A thin film glass was fixed in a reactionvessel and Fe(NH₄)₂(SO₄)₂ was added to the carbon nanotube-containingsolution to a concentration of 0.1 M and light irradiation with thewavelength (λ1, λ2, or λ3) to the substrate was carried out for 10minutes. After the carbon nanotube bearing the deposited metal wasaccumulated on the substrate, the carbon nanotube was washed withsulfuric acid and subjected to Raman spectroscopic measurement in theradial breathing mode to determine the chiral vector of the depositedcarbon nanotube. In the portion to which the light irradiation withwavelength of λ1 was carried out, it was found that the carbon nanotubehad the chiral vector (9, 1). Also, in the portion to which the lightirradiation with wavelength of λ2 was carried out, it was found that thecarbon nanotube having the chiral vector (11, 3) and (13,10) wascollected, and in the portion to which the light irradiation withwavelength of λ3 was carried out, it was found that the carbon nanotubehaving the chiral vector (13, 1) was collected. Accordingly, the carbonnanotube having the specific chiral vector could be separated andpurified.

TABLE 1 Chiral No. mettalic/ semiconducting Band gap Diameter Ramanshift λ1 (1064 nm) (9, 1)sc 1.13 eV 0.76 nm 326.3 cm⁻¹ λ2 (785 nm) (11,3)sc 1.57 eV 1.01 nm 244.6 cm⁻¹ (13, 10)m 1.58 eV 1.59 nm 156.4 cm⁻¹ λ3(514 nm) (13, 1)sc 1.17 eV 1.07 nm 231.8 cm⁻¹

Example 3

FIG. 9 shows a drawing of an experiment carried out similar to that inthe above-mentioned Example 2 with additional steps of flowing thecarbon nanotube-containing solution and supplying the obtained carbonnanotube dispersion continuously. As a result, the carbon nanotube couldbe deposited selectively as similarly described above, resulting in atwo to ten times increase in the amount of the deposition.

Example 4

FIG. 10 shows a drawing of an experiment carried out similar to that inthe above-mentioned Example 3, except that the light irradiation sourcewas limited with a lithographic pattern mask (10 μm width). As a result,the carbon nanotube could be deposited space-selectively with thestructure selectivity as described above. Accordingly, the carbonnanotube having the specific chiral vector could be separated, purifiedand fixed on any desired position of a substrate.

FIG. 11 shows a process drawing of an experiment carried out similar tothat in the above-mentioned Example 2, except that a near-field probechip for light irradiation was employed. In this case, a carbon nanotubewas fixed position-selectively on a substrate surface with the chiralselectivity, in similar manner as described in Example 2, by setting thelight irradiation time so as to provide the pulsed light (10 ms).Consequently, a single or an optionally controlled number of the carbonnanotubes having the specific chiral vector could be fixed at anyposition.

INDUSTRIAL APPLICABILITY OF THE INVENTION

According to the method and apparatus of the present invention, a carbonnanotube having an uniform desired physical property (including at leasteither a diameter or a chiral vector) can be highly selectivelyseparated, concentrated, and purified by utilizing the characteristicstructural susceptive of the carbon nanotube. Further, a thin film ofthe carbon nanotube with high purity separated by the above-mentionedmethod is useful as a next generation material for optical andelectronic devices in the electronics and energy field.

1. A method of separating, concentrating, or refining a carbon nanotubehaving a desired physical property from a sample solution, wherein thedesired physical property includes at least one of a diameter or achiral vector, the method comprising: a) irradiating light to the samplesolution containing carbon nanotubes in the presence of metal ions, sothat the metal ions are respectively reduced and deposited on the carbonnanotubes, and b) selecting the carbon nanotubes having the desiredphysical property by applying a predetermined magnetic field orchromatography to the carbon nanotubes so as to precipitate the carbonnanotubes with the desired physical property.
 2. The method according toclaim 1, wherein said carbon nanotube has a single-walled structure. 3.The method according to claim 1, wherein said light has a certainwavelength within a range covering from the near infrared region to theultraviolet region.
 4. The method according to claim 3, wherein saidlight is monochromatic light or laser light having said wavelength. 5.The method according to claim 1, wherein the metal ions are selectedfrom the group consisting of alkali metals; alkaline earth metals;transition metals selected from the group consisting of Group IIIA toGroup VIIA elements, Group VIII elements, and Group IB elements; andrare earth elements.
 6. The method according to claim 1, wherein thestep b) is carried out by applying a predetermined magnetic field tosaid carbon nanotube so as to precipitate the carbon nanotube with thedesired physical property.
 7. The method according to claim 1, whereinthe step b) is carried out by chromatography.
 8. The method according toclaim 1, wherein said sample further contains a surfactant.
 9. Themethod according to claim 8, wherein said surfactant is selected fromthe group consisting of sodium dodecyl sulfate, sodiumdodecylbenzenesulfonate, Triton X, alkylsulfonates, sodiumpolyoxyethylene alkyl ether sulfate, benzalconium chloride,alkyltrimethylammonium chloride, benzyltrimethylammonium chloride, nonylphenol ethoxylate, octyl phenyl polyoxyethylene ether, laurylpolyoxyethylene ether, and cetyl polyoxyethylene ether.
 10. The methodaccording to claim 1, wherein said sample is a water-based dispersion oran aqueous solution of the carbon nanotubes.
 11. The method according toclaim 1, wherein said carbon nanotubes are surface modified with asaturated or unsaturated carbon chain molecule having a carboxyl groupor an amino group as a substituent in the molecule through a covalentbond, an ionic bond, a hydrogen bond, or an intermolecular interaction.12. The method according to claim 1, wherein said sample solutionfurther containing a metal ion and an electron donor.
 13. The methodaccording to claim 12, wherein said solution contains the metal ion at aconcentration of 0.001 to 10%.
 14. The method according to claim 12,wherein said solution contains the electron donor at a concentration of0.001 to 10%.
 15. The method according to claim 12, wherein saidelectron donor is selected from the group consisting of alcohols,amines, arginine, benzaldehyde, hydrazine, carboxylic acids, aminoacids, toluene, alkylbenzenes, terpenes, ethers, silanes, and thiols.